Fluidized bed combustor

Abstract

A method of starting up a fluidized bed combustor in which a gas containing oxygen is passed from an outlet beneath the level of the slumped bed to cause a spouting action above the level of the slumped bed. Liquid fuel is supplied from a nozzle adjacent to or located within the spout, and an ignition source applied to the bed. The liquid fuel and gas containing oxygen supply are regulated so as to fluidize at least part of the bed adjacent to the liquid fuel outlet and to obtain a controlled rise in the temperature of the bed until the hot fluidized condition is reached.

We claim: 
     
       1. A method of starting up a fluidized bed combustor comprising the steps of: (a) passing an oxygen containing gas from an outlet beneath the surface of a slumped bed of particulate material to cause a spout zone of particulate material above the surface of the slumped bed;   (b) introducing liquid fuel from a nozzle within the bed into the effective spouting zone of the bed whereby a mixture of liquid fuel and oxygen containing gas is rapidly transported through the bed to the upper surface of the bed;   (c) igniting the liquid fuel/oxygen containing gas mixture above the surface of the bed;   (d) after ignition passing an oxygen containing gas into the bed to thereby obtain a controlled rise in the temperature of the bed until the entire bed is fluidized; and   (e) decreasing the flow of oxygen containing gas causing the spout simultaneously with said controlled temperature rise and stopping the flow of oxygen containing gas causing the spout when the entire bed is fluidized.   
     
     
       2. A method according to claim 1 in which the oxygen containing gas in step (a) is introduced around the periphery of the nozzle to thereby form an annular spout. 
     
     
       3. A method according to claim 1 or claim 2 in which the liquid fuel is supplied to the nozzle by feeding the liquid fuel to the interior surface of the nozzle so as to form a climbing film of liquid fuel which subsequently emerges from the nozzle outlet into the fluidized bed. 
     
     
       4. A method according to claim 1 where step (d) and step (e) are performed simultaneously by passing an oxygen containing gas into the bed at a steadily increasing rate until the entire bed is fluidised while simultaneously decreasing the flow of oxygen containing gas causing the spout. 
     
     
       5. A method according to claim 1 in which the liquid fuel is injected in the form of a fine spray into the oxygen containing gas and passing the mixture through the outlet and into the spout. 
     
     
       6. A method according to claim 1 in which liquid fuel is fed to the bed for a short time prior to igniting the liquid fuel. 
     
     
       7. A method according to claim 1 in which the liquid fuel is kerosene or gas oil. 
     
     
       8. A method according to claim 1 in which the oxygen containing gas of step (b) is air. 
     
     
       9. A method according to claim 1 in which the fluidized bed combustor comprises a distributor plate for supplying the oxygen containing gas of paragraph (d) to the bed, the bed lying above the distributor plate. 
     
     
       10. A method according to claim 1 in which the liquid fuel is ignited by means of an auxiliary burner, a spark ingiter or by passing propane gas and air through the nozzle and igniting the resultant combustible mixture at the bed surface.